In most cases, the transmission channel between a transmitter and a receiver has a limited capacity and generates attenuations and multipath propagation. It is therefore necessary to optimize the processing of the signal in order to increase throughput and quality of service.
The technique called MIMO (Multiple Input Multiple Output) is well known in wireless communications for increasing channel capacity, in the presence of multipath propagation. Several reception and/or transmission antennas are used, so as to exploit the spatial diversity generated by the multiple propagation paths.
More recently, the MIMO technique has been extended to wired communications, in particular for PLC (Power Line Communication) systems.
For example, the article by Giovaneli, Honary and Farrell entitled “Improved space time coding applications for PLC channels”, International Symposium on Power Line Communications and its applications, 2003, is dedicated to four-wire three-phase electrical networks.
The gain in terms of channel capacity is set out for example in “MIMO capacity of inhome PLC links up to 100 MHz”, IEEE WSPLC 2009, by Hasmat and Pagani.
In a MIMO type system, each receiving sensor is affected by noise, thereby corrupting the transmitted data.
In a wireless system, the various reception antennas are not physically connected, and are located at a distance from one another to benefit from spatial diversity. Thus, the noise signals received on the reception antennas are independent and uncorrelated.
Since the MIMO technique for a wired system is closely derived from that for a wireless system, it is generally considered that the noise signals received on the various reception sensors are also independent and uncorrelated in a wired system. The signal processing methods in the wired systems are therefore based on the hypothesis of independent and uncorrelated noise and no method has been developed to limit the effects of correlated noise in a MIMO system.
Nevertheless, the inventors have observed by laboratory-made measurements that the noise signals received on the various reception sensors are highly correlated in a wired MIMO system.
The result of this is that the conventional methods for increasing channel capacity in a MIMO system are not optimal since they are based on a false hypothesis.